The present invention relates to injection molding and more particularly to a process for injection molding contoured articles having multiple appliques.
Currently many injection molded articles include appliques—colored and/or textured layers covering the articles for decorative or functional purposes. For example, in the automotive industry, interior trim and instrument panel controls include colored appliques to enhance the appearance of the automobile's interior.
Appliques typically include a finished surface to provide an aesthetic appearance, for example a wood grain, and an unfinished surface to provide an interface for bonding a structural resin to the applique.
Frequently, it is desirable to combine multiple appliques on a single interior trim panel to minimize the number of interior panels in a vehicle. For example, a panel surrounding a radio in a car may include two appliques; an aesthetic wood veneer applique on the most prominent portion of the panel, and a black matte applique adjacent the digital display of the radio to minimize reflections from the display.
Prior art multiple applique panels are formed by an injection molding process wherein appliques are overlapped in a mold and a structural thermoplastic resin is injected over and around the appliques. An example of this process is illustrated in FIG. 1 where one applique 104 is positioned in overlapping relation to another applique 102 between molds 110 and 112. Both appliques have finished surfaces 101, 105 and unfinished surfaces 103, 107. A resin 106 is injected into the mold cavity around the appliques so that it pushes applique 104 upward and adjacent to applique 102 in region 108. Subsequently, finished surface 105 overlaps unfinished surface 103. During injection molding the unfinished surfaces 103, 107 bond to the resin 106. After the injection molded plastic cools, a panel including appliques 102 and 104 and the resin layer 106 is removed from the molds 110 and 112.
Although the injection molding process of the prior art produces a multiple applique panel, it suffers a number of shortcomings. Most significantly, the region where the appliques overlap one another is prone to peeling, detaching, and warping, as illustrated in region 108 of FIG. 2. In this region, the unfinished surface 103 frequently detaches from the finished surface 105, and in some cases, to such a degree that a consumer may peel applique 102 away from applique 104. In warm, humid southern climates, the frequency of such defects is significantly increased. Of course, such defects lead to distorted and aesthetically displeasing automotive trim. At a substantial cost, the manufacturer of such trim typically has to replace the trim if the product is under warranty.